This invention relates to a tension sensor and, in particular, to a tension sensor for measuring tension in a magnetic tape running along a predetermined path.
In recent years, many kinds of instruments, such as VTR's, audio tape decks, etc. employing a magnetic tape as a recording medium, have been widely used. In these instruments, a provision of a monitoring device to sense the tape tension is indispensable for the reproduction of a record of superior quality.
As a means of measuring the tape tension, those apparatus which are of a mechanical type or a force-displacement conversion type have so far generally been used, and particularly there has been employed a mechanism in which a tape guiding post is provided on one end of an arm which is rotatably supported by a bearing and biased in one direction by a resilient body such as a spring or the like and the tape tension is measured by sensing the rotational displacement of the arm which is caused by the tape tension which is in opposition to the biasing force of the spring or the like.
However, so far as depending on such a method as above, not only is the measurable range limited by the kind of resilient body used as a spring or the size of the turning arm but a detrimental effect due to a change of the measuring position with respect to the tape is also often caused because such a system uses a sensing displacement transformed from a force; in addition, such a system has a drawback in that it requires a wide space for displacement. Furthermore, since there are many cases requiring conversion of such a displacement into an electric signal, an increase in the number of constituent parts and cost occurs as well as making the precision in measurement questionable.
Other apparatus of the mechanical type have drawbacks of almost the same kind as above.
These tension sensors can rarely meet the requirements for miniaturization and performance improvements that are demanded today, and the development of a novel tension sensor is earnestly needed at the present stage.
An object of this invention is to solve such problems inherent in conventional tension sensors as described above and provides a novel tension sensor which is capable of accurately measuring tape tension in a wide range without inflicting any disturbance to the tape.